Various waveguide grating structures have already been described in the PCT applications PCT/EP94/02361 and PCT/CH98/00389. The beam guiding, however, is not optimal. The reflected beam of a first incident light wave coincides with the direction of a second incident light wave. The reflected light beam and the second incident light beam oppositely have the same direction, which may lead to perturbations. The PCT applications PCT/EP94/02361 and PCT/CH98/00389 do not illustrate how a waveguide grating sensor structure that consists of two-dimensionally arranged sensor locations may be read out in parallel in the case of detection free of marking. Parallel reading-out is, however, necessary in order to achieve a higher throughput.
In the European patent application EP 0 482 377 A2 the waveguide grating is illuminated with a focussing light field. A focussing light field is not suitable for simultaneous illumination of a two-dimensional array of waveguide grating sensors. Furthermore, there is no mention of a method for temperature compensation in this application.
In Sensors and Actuators B 38-39 (1997), 116-121, a sensor location and a reference location of the waveguide grating are illuminated using the multiplex method. Also there is shown no one-dimensional or two-dimensional beam divergence of the incident light beam.
The present invention achieves the object of creating an optical sensor which:
(1) simultaneously illuminates several one-dimensionally or two-dimensionally arranged sensor locations based on waveguide grating structures via suitable beam diverging optics;
(2) ensures the separation of light fields or light beams;
(3) produces light fields on a detector or detector array (e.g. pixel array detector), which do not superimpose on the detector or detector array;
(4) generates measurement signals on non-reflected light fields;
(5) generates measurement signals that have a low temperature dependence;
(6) carries out measurements in a scanning mode method without moving mechanics and with a large dynamic range;
(7) for determining the resonance location, evaluates the scan distribution (i.e. the light intensity measured in a certain detector range as a function of the scan parameter, and/or the light intensity measured in a certain detector range as a function of the detector coordinates) with a center of intensity method or with a data fit of a part of the scan distribution (region of the maximum, region of the maximal rise (gradient), region of the constant rise (gradient));
(8) generates referenced sensor signals by way of evaluating a signal path and at least one reference path;
(9) increases the measurement accuracy by way of scan averaging methods or resonance location averaging methods; and,
(10) permits the evaluation of micro-plates, micro-arrays and lab-on-chips.
The invention also suggests waveguide grating structure units that permit a separation of the incident, reflected, or diffracted light beams without the beam path having to be tilted with respect to the plane of incidence. Furthermore, the reading out of the four out-coupled modes TE+, TExe2x88x92, TM+, TMxe2x88x92 (notation: TE+: transversal electrical mode in (+x) direction (forward direction), TExe2x88x92: transversal electrical mode in the rearward direction, TM+: transversal magnetic mode in the forward direction, TMxe2x88x92: transversal magnetic mode in the rearward direction) may be effected on a single one-dimensional or two-dimensional position-sensitive detector (e.g. pixel array detector), wherein preferably between the detector and the waveguide grating structure there are arranged lens optics. If one-dimensional or two-dimensional arrays of waveguide grating structure units (for example arrays of sensor locations) are used, as they are for example applied with micro-plates or micro-arrays, it is recommended to operate with a two-dimensional pixel array detector, since all out-coupled and/or radiated light waves may be incident on the two-dimensional detection surface. The arrays of waveguide grating structure units (for example arrays of sensor locations) may be arranged on a round or polygonal (rectangular) disc (plate) in a Cartesian, matrix-like, or circular-(ring)-shaped manner.